Coating fibers using directed vapor deposition

ABSTRACT

A method of making a fiber tow coating is provided. The method includes providing a fiber tow selected from the group consisting of carbon and silicon; and applying an oxide-based fiber interface coating onto the fiber tow using directed vapor deposition or other like deposition method.

CROSS REFERENCE TO RELATED APPLICATIONS

The present patent document is a continuation of U.S. patent applicationSer. No. 14/876,270, filed Oct. 6, 2015, which claims the benefit ofpriority to U.S. Provisional Patent Application No. 62/060,662, filedOct. 7, 2014. The disclosures of the aforementioned patent documents arehereby incorporated by reference.

TECHNICAL FIELD AND SUMMARY

The present disclosure relates to fiber coatings and, in particular, todepositing a coating or coatings on a multifilament fiber tow materialusing directed vapor deposition, chemical vapor infiltration, or similarprocesses.

Economic and environmental concerns, i.e. improving efficiency andreducing emissions, are driving forces behind the ever increasing demandfor higher gas turbine inlet temperatures. Designers of gas turbineengines recognize that a limitation to the efficiency and emissions ofmany gas turbine engines is the temperature capability of hot sectioncomponents (examples include, but are not limited to blades, vanes,blade tracks, and combustor liners). Technology improvements in cooling,materials, and coatings are required to achieve higher inlettemperatures. As the temperature capability of Ni-based superalloys hasapproached their intrinsic limit, further improvements in theirtemperature capability have become increasingly difficult. Therefore,the emphasis in gas turbine materials development has shifted to thermalbarrier coatings (TBC) and next generation high temperature materials,such as ceramic-based materials.

SiC/SiC CMCs are prime candidates to replace Ni-based superalloys forhot section structural components for next generation gas turbineengines. The key benefits of SiC/SiC CMC engine components are theirexcellent high temperature, mechanical, physical, and chemicalproperties which allow gas turbine engines to operate at much highertemperatures than the current engines having superalloy components.SiC/SiC CMCs also provide the additional benefit of damage tolerance,which monolithic ceramics do not possess. The damage tolerance ofSiC/SiC may be a result of a fiber interface coating that may result incrack deflection and crack bridging. During operation the prior artfiber interface coatings may be attacked by the environment which mayreduce or negate their effectiveness to provide damage tolerance. Theintroduction of fiber interface coatings that are inert under theanticipated engine environment would greatly benefit these materialsystems. These systems would enhance life and reduce risk of materialembrittlement.

The current SOA fiber interface coating chemistry of boron nitride orcarbon has limited stability in an oxidizing/combustion environment.Damage during engine operation may result in exposure of the fiberinterface to an oxidizing environment. This exposure may result in lossof the interface coating, or the formation of low temperature oxidesthat react with the matrix.

An illustrative embodiment of the present disclosure provides a methodof fiber tow coating which comprises the steps of: providing a fiber towmade of a material that is selected from the group consisting at leastone of a carbon material and a silicon material; and applying anoxide-based fiber interface coating onto the fiber tow using directedvapor deposition.

In the above and other illustrative embodiments, the method may furthercomprise the steps and limitations of: the oxide-based fiber interfacecoating being a ceramic oxide; the ceramic oxide being selected from thegroup consisting of a rare earth monosilicate, a rare earth disilicate,barium strontium aluminosilicate, mullite, yttrium aluminum garnet, anda rare earth monazite; a base of the rare earth monosilicate and therare earth disilicate being selected from the group consisting ofscandium, yttrium, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, and lutetium; a base of the rareearth monazite being selected from the group consisting of lanthanum,cerium, praseodymium, and neodymium; the fiber being a filament tow; thefilament tow being a multifilament tow; the material of the filament towbeing selected from the group consisting at least one of siliconcarbide, silicon nitride, Si—N—C, and Si—O—C; the coating having athickness of about 0.05 to about 2 microns; the fiber being selectedfrom the group consisting of a woven fabric, a woven preform, alaminated preform, a wide tape of monofilament, and a multifilament; thecoating being applied using a single source or a multiple source target;the coating being selected from the group consisting of a singlecomposition, a graded composition, and a layered structure of aplurality of compositions; the deposition includes multiple depositionzones; the steps of passing the fiber through a deposition zone aplurality of times; the coating has a variable thickness; applying acoating onto the oxide-based fiber interface coating, wherein thecoating is selected from the group consisting of silicon carbide,silicon nitride, Si—N—C, and Si—C—O; applying another oxide-basedcoating onto the coating; the fiber being coated on a continuous feed;the continuous feed being a reel system; the reel system applies tensionto spread the fiber to improve infiltration; applying a coating onto theoxide-based fiber interface coating wherein the coating is applied priorto being taken up by a fiber take-up reel; and the coating includes afiber sizing or a preceramic polymer.

Another illustrative embodiment provides a method fiber coating whichcomprises the steps of: providing a fiber tow made of a material that isselected from the group consisting at least one of a carbon material anda silicon material; and applying an oxide-based fiber interface coatingonto the fiber tow using chemical vapor infiltration.

Another illustrative embodiment provides a method of fiber tow coatingwhich comprises: providing a fiber tow made of a material that isselected from the group consisting at least one of a carbon material anda silicon material; applying a fiber interface coating selected from thegroup consisting of a boron nitride or carbon onto the fiber tow using aprocess selected from the group consisting of directed vapor depositionand chemical vapor infiltration; and applying a second layer on theoxide-based fiber interface coating wherein the second layer is selectedfrom a group consisting of a Y disilicate, a Yb disilicate, bariumstrontium aluminosilicate, and lanthanum monazite.

Additional features and advantages of these methods will become apparentto those skilled in the art upon consideration of the following detaileddescription of the illustrated embodiment exemplifying the best mode ofcarrying out these methods as presently perceived.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure will be described hereafter with reference to theattached drawing which is given as a non-limiting example only, inwhich:

FIG. 1 is a schematic view of an illustrative fiber deposition system.

FIG. 2 is a block diagram depicting the method of applying anoxide-based fiber interface coating onto the fiber towing using directedvapor deposition (DVD).

FIG. 3 is a block diagram depicting the method of applying anoxide-based fiber interface coating onto a fiber tow using chemicalvapor infiltration.

FIG. 4 is a block diagram depicting the method of applying boron nitrideor carbon onto the fiber and then applying a second layer on the oxidebased fiber interface coating.

The exemplification set out herein illustrates embodiments of themethods and such exemplification is not to be construed as limiting thescope of the methods in any manner.

DETAILED DESCRIPTION

The present disclosure provides oxide-based fiber tow interface coatingsfor carbon or ceramic multifilament tows including silicon carbide(SiC), silicon nitride, Si—N—C, Si—O—C, and oxide fibers. The siliconcarbide and oxide base include, but are not limited to, the productsproduced by Nippon Carbon, Ube Industries, ATK-COI Ceramics, SpecialtyMaterials and 3M, for example. In an illustrative embodiment, the fibercoating thickness may range from about 0.05 microns to about 2 microns.

The proposed coating would be applied to a multifilament tow usingdirected vapor deposition (DVD) techniques. Woven fabrics, wovenpreforms, laminated preforms or wide tapes of monofilament ormultifilament may be coated. The current DVD process can apply a rangeof fiber interface coating compositions that includes the currentstate-of-the-art boron nitride, carbon interfaces, and ceramic oxides.The ceramic oxides may include, but are not limited to, the rare earthmonosilicates/disilicates (scandium, yttrium, lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetiumbased), barium strontium aluminosilicate (BSAS), BAS, SAS, mullite,yttrium aluminum garnet (YAG), and rare earth monazites (lanthanum,cerium, praseodymium, or neodymium based).

A schematic view of an illustrative fiber tow deposition system 2 isshown in FIG. 1. System 2 shows an illustrative fiber 4 strung between afiber source reel 6 and a take-up reel 8. Vaporization input e-beamlaser 10 emits beam 12 toward source material target 14 to create vapordeposition area 16. Fiber 4 passes through area 16 depositing vaporizedsource material (illustrated by reference number 18) onto it creatingthe coating. It is appreciated that option source materials 20, 22, anda heat source 24 may be added. In addition, an optional secondarycoating system 26 may be added to coat fiber 4.

The coating may be applied using a single source or multiple sourcetargets within the DVD process. The proposed coating may also be asingle composition, a graded composition, or a layered structure of twoor more compositions. In a continuous process, multiple deposition zonesmay be used to apply the coatings. The material to be coated may also bepassed through the same deposition zone more than once by incorporationof appropriate rollers or other devices. The reaction zone cross sectionand size may be varied to vary the coating thickness. This may beespecially useful for multi-layer coatings with different depositionkinetics or different target thicknesses. Layers of silicon carbide,silicon nitride, Si—N—C, and Si—C—O may also be applied on top of or inbetween the layers.

In a single layer fiber coating an oxide may be selected. This coatingmay include Y or Yb disilicate, BSAS, or lanthanum monazite. Theproposed coating may also include a layered structure that can be acombination of the oxides listed above or of more traditional coatingsystems. For example, the first layer may consist of a boron nitride orcarbon interface that is deposited using DVD or chemical vaporinfiltration. The second layer may include Y or Yb disilicate, BSAS, orlanthanum monazite.

In one example, as shown in FIG. 2, the coatings are applied using a DVDprocess. In addition to the DVD process, traditional fiber coatingtechnologies (i.e. chemical vapor infiltration) may be incorporated intothe process to create multilayer fiber coatings.

As described in FIG. 2, method 100, the process described herein mayutilize directed vapor deposition (DVD), which is a novel type ofelectron beam-physical vapor deposition (EB-PVD). In a step 110, thefiber tow may be provided. The fiber tow may be an uncoated fiber tow ora coated fiber tow. In a step 120, an oxide based fiber interfacecoating may be applied onto the fiber tow using DVD. DVD may use anelectron beam to form a vapor plume including the coating components,and a stream of gas is used to direct the vapor plume. Due to the gasstream, the vapor plume may be directed to internal cavities ofcomponents and DVD may be used to deposit the coating on internalsurfaces of the components, such as surfaces of cooling channels in ablade or vane. The DVD process may require ingots of the target coatingcomposite to be used. As the ingot evaporates the vapors, such as oxidevapors, may redeposit on the substrate. In the present application, twoingots may be used to control the rate of vaporization of each ingot toobtain the target coating composition. Two separate ingots may be usedto account for vapor pressure differences. The process described hereinmay arrange the ingots and fibers to make a continuous process. Thefibers may pass through the chambers in a continuous motion.

For the DVD coatings, a vapor pressure at deposition temperature of eachelemental constituent may be calculated using standard thermodynamicpractices.

As shown in FIG. 3 method 200, the fiber tow may be coated usingchemical vapor infiltration. In a step 210 of the method 200 an uncoatedfiber tow or a coated fiber tow may be provided. In a step 220 of themethod 200, an oxide based fiber interface coating may be applied usingchemical vapor infiltration also referred to as chemical vapordeposition (CVD). CVD may deposit a gaseous/vaporous coating onto thefiber tow to bond the coating onto the fiber tow in a continuousprocess.

As shown in FIG. 4 method 300, a second layer of coating may be appliedon the fiber interface coating. In a step 310 of the method 300, a fibertow may be provided. The fiber tow may have previously been coatedaccording to the methods described in FIGS. 2 and 3. In a step 320,boron nitride or carbon may be applied onto the fiber. In a step 330 ofthe method 300, a second layer may be applied to the fiber tow. Thesecond layer may be applied by either CVD or DVD as described above.

The proper sources would be selected to deposit the selectedcomposition. The source may be a single source or multiple sources. Thiswill depend on the vapor pressures and desired kinetics of the reaction.The source material may also be fabricated using standard ceramicprocessing, or by induction melting.

The source material may be heated using e-beam, laser, or by aninduction melting approach. Induction melting may be introduced as theonly heating source, or it can be combined with e-beam and laser. Theinduction source may be applied to a single or multiple sources.

The vaporized material is carried to the multifilament tow, by a carriergas. The carrier gas may be inert or a reactive species.

A multifilament tow may be coated in this process. The process may alsoaccommodate a continuous feed. For example, the continuous feed may be areel system. The reel system may apply tension to spread the fiber toimprove infiltration. The source fiber can be fed by a reel system thatapplies tension to spread the fiber tow for improved infiltration. In acontinuous operation, the fiber tow may be coated by an optionalsecondary coating. This secondary coating may be applied prior to thefiber take-up reel. The secondary coating may include, but is notlimited to, a fiber sizing or preceramic polymer. A coating may beapplied onto the oxide-based fiber interface coating where the coatingmay be applied prior to being taken up by a fiber take-up reel. Thecoating may have a thickness of between about 0.05 microns and about 10microns. Specifically the thickness may be between about 0.05 micronsand about 2 microns.

The interface coatings applied using the DVD process have improvedstability in an oxidizing/combustion environment. This improvement mayprovide: (1) increased life after matrix cracking; (2) increased designmargin, and improved fiber interface coatings would allow designs tolocally exceed matrix cracking; (3) increased life after the loss of anenvironmental barrier coating; and (4) avoidance of low temperatureoxidation embrittlement.

Additional benefits may further include: (1) reduced cycle time forinterface coating depositions; (2) increased composition window whencompared to current processing boron nitride fiber interface coatings;(3) coating system that can be applied to high oxygen content SiC basefibers (CG Nicalon, Tyranno ZMI); (4) improved thermal expansion matchwith the fiber and/or matrix; and (5) increased shear strength that canimprove load sharing in a ceramic matrix composite. If the strength ofthe fiber coating is limiting interlaminar properties, a strongercoating may also improve interlaminar properties.

Although the present disclosure has been described with reference toparticular means, materials, and embodiments, from the foregoingdescription, one skilled in the art can easily ascertain the essentialcharacteristics of the present disclosure and various changes andmodifications may be made to adapt the various uses and characteristicswithout departing from the spirit and scope of the present invention asset forth in the following claims.

What is claimed is:
 1. A coated fiber tow comprising: a fiber towcomprising a material selected from the group consisting of at least oneof a carbon material and a silicon material; an oxide-based fiberinterface coating on the fiber tow; and a Si-based coating on theoxide-based fiber interface coating, wherein the Si-based coatingcomprises a material selected from the group consisting of siliconcarbide, silicon nitride, Si—N—C, and Si—C—O.
 2. The coated fiber tow ofclaim 1, wherein the oxide-based fiber interface coating comprises aceramic oxide.
 3. The coated fiber tow of claim 2, wherein the ceramicoxide is selected from the group consisting of a rare earthmonosilicate, a rare earth disilicate, barium strontium aluminosilicate,mullite, yttrium aluminum garnet, and a rare earth monazite.
 4. Thecoated fiber tow of claim 3, wherein a base of the rare earthmonosilicate and a base of the rare earth disilicate is selected fromthe group consisting of scandium, yttrium, lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.5. The coated fiber tow of claim 3, wherein a base of the rare earthmonazite is selected from the group consisting of lanthanum, cerium,praseodymium, and neodymium.
 6. The coated fiber tow of claim 1, whereinthe oxide-based fiber interface coating comprises yttrium disilicate,ytterbium disilicate, barium strontium aluminosilicate, or lanthanummonazite.
 7. The coated fiber tow of claim 1, further comprising asecond coating on the oxide-based fiber interface coating, the secondcoating comprising yttrium disilicate, ytterbium disilicate, bariumstrontium aluminosilicate, or lanthanum monazite.
 8. The coated fibertow of claim 7, wherein the Si-based coating is disposed on the secondcoating.
 9. The coated fiber tow of claim 7, wherein the Si-basedcoating is disposed between the oxide-based fiber interface coating andthe second coating.
 10. The coated fiber tow of claim 1, wherein thefiber tow is a multifilament tow.
 11. The coated fiber tow of claim 1,wherein the silicon material is selected from the group consisting ofsilicon carbide, silicon nitride, Si—N—C, and Si—O—C.
 12. The coatedfiber tow of claim 1, wherein the fiber tow is selected from the groupconsisting of a woven fabric, a woven preform, a laminated preform, awide tape of monofilament, and a multifilament.
 13. The coated fiber towof claim 1, wherein the oxide-based fiber interface coating comprises athickness in a range from about 0.05 micron to about 2 microns.
 14. Thecoated fiber tow of claim 1, wherein the oxide-based fiber interfacecoating and the Si-based coating are deposited by directed vapordeposition.
 15. The coated fiber tow of claim 1, wherein the oxide-basedfiber interface coating and the Si-based coating are deposited bychemical vapor deposition.